The pesticide methoxychlor is presently in wide use as a substitute for the banned DDT. Biochemical research has established that the pesticide has estrogenic action; however, very little data are available concerning the effects of methoxychlor on mammalian reproductive organs. Reproductive systems of immature mice as well as other mammals appears highly sensitive to estrogenic action. This study proposes to measure the estrogenic and/or toxic effects of methoxychlor on the anatomy, physiology and cell biology of the reproductive system in neonatal and adult mice. To accomplish this goal, neonatal mice of Swiss-Webster strain will be exposed to methoxychlor and the following information collected: a) morphology of oviduct, uterus, cervix, vagina and ovaries, b) regularity of estrous cycles and onset of reproductive senescence, c) type of vaginal cornification, d) ovarian function and LH and FSH levels in ovariectomized mice, and e) patterns of secretions of proteinaceous molecules by endometrial cells in adults. The results obtained from this proposal will be valuable in establishing the mechanism of methoxychlor action in the reproductive organs of exposed newborn and adult mammals. In addition, the new data will be very useful in determining the impact of methoxychlor's wide use in the environment on the reproductive capabilities of non-target species and humans who, as a result of occupational exposure, may come in daily contact with this chemical.